Video security system

ABSTRACT

The invention provides a video security system for monitoring a plurality of locations simultaneously. In one embodiment, the system includes a text insertion means connected between a video camera and monitor, a control means connected to the text insertion means, and a playback means operatively associated with the text insertion means and control means. Other embodiments include a video camera substitution system having a fixed video camera and a pan-tilt video camera and a video recorder substitution system having a plurality of alternate VRDs. In another embodiment, the system includes a programmable equalizer having a plurality of video input devices, a video output receiver, a switch connected between the input devices and receiver, a variable equalizer connected between the switch and receiver, and a controller storing line loss parameters for each input device, thereby providing equalization among a plurality of video cameras, monitors, and video signal recording devices.

FIELD OF THE INVENTION

The present invention relates to a video security system particularly,although not exclusively, envisaged for use in the monitoring of aplurality of locations, such as, in a building, for example, a casino.

More particularly the present invention relates to a video securitysystem (VSS) particularly directed at addressing the difficulties whichprior art security systems generally experience, such as:

-   1. avoiding text information obliterating important video    information;-   2. switching repeatedly between two or more views of interest with a    single camera;-   3. dealing with equalisation problems between video cameras, video    monitors and/or VCRs or other video signal recording device;-   4. overcoming the problem of tracking an object with a camera when    it approaches a 360° endstop;-   5. overcoming the problem of pan/tilt camera control when zoomed    out;-   6. controlling the camera to move rapidly between two or more views    of interest; and,-   7. VCR management issues including: failure of VCRs; change-over    delay in VCR cassettes; and dealing with camera failure and    replacement.

It is to be kept in mind that the purpose of the video security systemof the present invention is to provide video images regarding eventspertaining to the security of a building or the like and to allow thoserecorded video images to be presentable in a court of law as irrefutableevidence of the events which took place.

Hereinafter the term “VCR” ill be used to denote any form of videosignal recording and/or playback device (referred to as a “VRD”) and mayinclude a video cassette recorders or any optical or digital recordingmedia suitable for recording video signals.

BACKGROUND OF THE INVENTION

1. “Text Overlay”—In the field of video security systems it is known tointroduce text into the video signal to provide a real time record ofthe details of the event which is being monitored. A disadvantage ofsuch prior art systems is that the information is introduced into thevideo part of the video signal and hence over-writes a part of the videopicture which would have otherwise been recorded. The present inventionovercomes this by inserting the text into the non-video part of thevideo signal.

2. “Toggle”—The secret to the success of switching between a pluralityof fixed locations is to be able to quickly and easily identify two, ormore, viewing locations “on the fly”. This is particularly for viewingtargets of short term or temporary interest.

In the context of the present invention “on the fly” means to beperformed whilst the VSS is in its normal mode of operation and withoutinterrupting the normal operation of the VSS.

Also, in the context of the present invention the feature of “switchingback and forth between two (or more) viewing locations” is referred toas “toggling” between the viewing locations.

However, where the operator is interested in two or more specificlocations within the viewing region the PTZ camera must be adjustedmanually between these locations. This is quite laborious and tediousfor the person operating the PTZ camera since it involves adjusting thepan, tilt, zoom and focus setting for the PTZ camera.

We have discovered that this can be overcome by recording the PTZ camerasettings corresponding to the desired locations of viewing into a cameraposition controller and switching between the locations by recalling thesettings for each of the viewing locations. The PTZ camera then iscontrolled by the camera position controller to adjust itself betweenthe desired locations.

“Preset” PTZ camera viewing locations are known and are widely used,however, they require the operator to make several control operations toset each viewing location and at least two control operations to switchfrom one viewing location to another.

This is particularly inconvenient in a viewing region such as in acasino where there are many potential targets, where there is arequirement to quickly and reliably set viewing locations and where itis critical to be able to switch between typically two targets. The twotargets would typically be a suspected felon and a handbag which it issuspected that the felon will steal. Typically, there is an accompliceto be monitored as well. Usually the accomplice in this scenario is awoman who collides briefly with the felon and takes the handbag once thehandbag has been stolen. Hence, the task of the operator of the VSS isto first monitor the suspected felon and the sandbag by toggling backand forth between the two and once the handbag has been stolen tomonitor the felon and then to monitor a person who may collide with thefelon.

In the present invention we have determined a way to enable the operatorto operate a single control function (such as by a control button) toset, update and toggle between two or more viewing locations. This mostreliably and efficiently allows the operator to monitor the targets.

3. “Signal Equalisation”—Prior art video security systems have theproblem that equalisation of the video signals must be provided for eachvideo camera. That is, there must be one equalisation unit for eachcamera.

We have overcome this difficulty by having one equalisation unit foreach video monitor and automatically adjusting the equalisation unit foreach video camera as it is connected to the monitor. Hence, only afraction of the number of equalisation units is required.

4. “Rotation End Stops”—Another problem of existing video securitysystems is that most of the cameras which they use are only able torotate through about 360°. Hence, when following a target the camera canreach its end stops and have to unwind before it can continue to followthe target. By the time that the camera has unwound the target may nolonger be in sight.

We have overcome this problem in an inexpensive way by using a cableloop wound in a way that it is able to twist 3 to 4 times, and hence thecamera can be rotated through an angle of about 1000°. A control unit ofthe camera then is programmed to return the camera to about the centreof its rotation when the camera is not being used to track a target.Hence, the camera is relatively unlikely to reach its end stops duringnormal use.

5. “Pan Speed vs Zoom”—Prior art vide cameras have the further problemthat when the lens is zoomed in (that is viewing an object at adistance) the rate of pan per degree of arc is the same as when the lensis zoomed out. Hence, it becomes difficult to accurately control the panof the lens when zoomed in. Also, it is difficult to observe the imageof the camera during panning when zoomed in because it is usuallyblurred or indistinct due to the pan speed being too high.

We have overcome this problem by linking the pan speed to the zoomposition of the lens so that the rate of pan per degree of arc decreasesas the lens is zoomed in and increased as the lens is zoomed out.

6. “Accuracy of Camera Positioning”—Conventional camera positioncontrollers have problems in maintaining accuracy of positioning of thevideo camera (for viewing a target in a predetermined location) whilstseeking maximum speed of movement of the video camera. That is, in therace for maximum speed, so that one camera can be used to monitor two ormore locations, the position controller is not able to keep accuraterecord of the location of the camera. This is primarily due to problemsencountered in rapid changes in acceleration.

We have overcome this problem by designing a camera position controllerwhich ensures that there is a minimum period of substantially zeroacceleration before any change in acceleration direction. This thusavoids large changes in momentum introduced when switching abruptly fromacceleration to deceleration.

7. “Non-Recording Time”—Another problem of prior art video securitysystems is that during the times referred to in item 7 of the Field ofthe Invention no recording can occur. Hence, the video security systemcan not record all events which its cameras see. For example, in a videosecurity system-having 125 VCRs there would be a minimum recording timeloss of 2 hours per day due only to the time taken to change over tapes(assuming the operation takes 30 seconds and each tape records for 8hours). There is further loss of recording when an operator deliberatelytakes a VCR off-line in order to review one of the tapes.

In order to overcome these periods of lost recording we have designed aVSS to automatically manage the VCRs and cameras so as to ensure thateach target is monitored continuously and each video signal is recordedcontinuously. This is achieved by using backup video cameras and backupVCRs and by providing a log of the camera and VCR associated with eachviewed target.

SUMMARY OF THE INVENTION

Therefore it is an object of the present invention to provide a videosecurity system to overcome the above identified problems.

1. It is an object of the present invention to provide a text insertionsystem which enables storage of text other than in the part of the videosignal which corresponds to the video image.

In accordance with another aspect of the present invention there isprovided a text insertion system for a video security system having avideo camera and a video monitor and/or a VRD capable of operation in arecord mode, the text insertion system comprising:

-   -   a text insertion means connected between the video camera and        the video monitor and/or VRD for inserting a text signal into a        video signal received from the video camera for display on the        video monitor and/or recordal by the VRD, the insertion of the        text signal being timed within the back porch of the video        signal so that the text signal does not alter the visible part        of the video frame of the video signal;    -   a control means connected to the text insertion means, the        control means generating the text signal and sending the text        signal to the text insertion means; and,    -   a playback means operatively associated with the text insertion        means and the control means, the playback means responding to        the text signal portion of the video signal, the playback means        having a text signal display means for rendering the text signal        visible on the video monitor, and a text signal hiding means for        rendering the text signal non-visible on the video monitor, the        text signal display means and the text signal hiding means being        operable by a person using the text insertion system to allow        alternating between showing text corresponding to the text        signal on the video monitor and showing on the video monitor        that part of the video frame which would otherwise be obscured        by the text, and the playback means being able to make the text        signal visible or hidden during both recording and playback        modes of operation of the VRD.

2. Therefore, it is an object of the present invention to provide a PTZcamera for a video security system which is capable of being controlledby an operator to toggle between a plurality of desired camera viewinglocations.

In accordance with one aspect of the present invention there is provideda PTZ camera for viewing a plurality of targets within a regionsurrounding the PTZ camera, the PTZ camera comprising:

-   -   a video lens and camera for viewing the targets and sending a        video signal to a video monitor and for a VRD;    -   a zoom control means for controlling the video lens for viewing        the targets;    -   a focus control means for focusing the video lens for viewing        the targets;    -   a pan control means for panning the video lens and camera for        viewing the targets;    -   a tilt control means for tilting the video lens and camera for        viewing the targets; and,    -   a camera position control means for controlling the video lens,        the zoom control means, the focus control means, the pan control        means and the tilt control means, the camera position control        means having a first current position means for storing the        settings corresponding to the location of one of the targets,        and a second current position means for storing the settings        corresponding to the location of another one of the targets, the        camera position control means being operable to switch control        between the first current position means and the second current        position means for allowing viewing to switch between two        targets of present interest, wherein the first current position        means and the second current position means are operatable to        set, update and toggle the view on the video monitor between the        two locations of the targets.

3. It is an object of the present invention to provide a transmissioncable equalisation system for a video security system having a pluralityof video cameras and a video monitor and/or a VRD capable of operationin a record mode, the transmission cable equalisation system comprising:

-   -   a selector means connected between the video cameras and the        video monitor and/or VRD for selecting video signals from the        video cameras to be directed to the video monitor and/or VRD so        that the video signal from one video camera is display on the        video monitor and/or recorded on the VRD at a time;    -   an equaliser means connected between the selector means and the        video monitor and/or VRD for equalising the video signal from        losses caused by the nature of the connection between each of        the video cameras and the selector means; and,    -   a control means connected to the equaliser means and the        selector means, the control means having a reference means        having data quantifing the losses between each video camera and        the selector means, and the control means controlling the        equaliser means to compensate for the losses associated with        each video camera as its video signal is displayed on the video        monitor and/or recorded on the VRD so that the condition of the        video signal at the video monitor and/or VRD is equalised        substantially independent of the characteristics of the        connection between the video camera and the selector means so        that only one equalisation means is required per video monitor        and/or VRD instead of one equalisation means per video camera.

4. It is an object of the present invention to provide a video camerawhich is controllable to rotate through a fixed angle which is greaterthan 360°.

In accordance with a still further aspect of the present invention thereis provided a video camera for a video security system, the video cameracomprising:

-   -   a video lens for viewing a target and sending a video signal to        a video monitor and/or a VRD;    -   a transport mechanism upon which the video lens is mounted, the        transport mechanism being rotatable through a fixed azimuth        range of greater than 360° so that the video lens can view        targets which move through an azimuth range of greater than        360°; and,    -   a loop of electrical cables arranged to be able to twist through        an azimuth range of greater than 360°.

5. It is an object of the present invention to provide a video camerawhich is controllable to pan at a speed which changes corresponding tothe zoom setting of the camera.

In accordance with yet another aspect of the present invention there isprovided a video camera comprising:

-   -   a video lens for viewing a target and sending a video signal to        a video monitor and/or a VRD;    -   a zoom control means for controlling the video lens to see        targets at varying ranges from the video camera;    -   a pan control means for panning the video lens; and,    -   a control means for controlling the speed at which the video        lens is panned, the control means being able to set a relatively        slow pan speed when the zoom control means controls the video        lens to view a target which is relatively far from the video        lens and to set a relatively high pan speed when the zoom        control means controls the video lens to view a target which is        relatively close to the video lens so that both distant and        close targets can be panned over at substantially the same        speed.

6. It is an object of the present invention to provide a cameratransport mechanism which has a camera position control system formoving a camera rapidly between a plurality of viewing positions.

In accordance with a further aspect of the present invention there isprovided a camera transport mechanism for moving a video camera betweena plurality of viewing positions, the camera transport mechanismcomprising:

-   -   a platform for carrying a video camera;    -   a vertical axis drive unit attached to the platform for moving        platform about a vertical axis;    -   a horizontal axis drive unit attached to the platform for moving        the platform about a horizontal axis; and,    -   a camera position control system for recording the location of a        plurality of viewing positions and for controlling the movement        of the platform between said viewing positions, the camera        position control system being configured control the movement of        the platform so as to provide a minimum period during which        there is substantially zero acceleration between changes in        acceleration of the platform from acceleration to deceleration        so as to reduce the amount of rate of change of momentum        experienced by the platform and thus improve the accuracy of        determination of the position of the platform so as to more        accurately control the movement of the platform and hence the        video camera between the viewing positions.

7. It is an object of the present invention to provide a video camerasubstitution system for ensuring that video images are always availableto be reviewed and/or recorded even in the event of the failure of avideo.

In accordance with a still further aspect of the present invention thereis provided a video camera substitution system for a video securitysystem having a fixed video camera for viewing a target area, a pan-tiltvideo camera capable of orientation to substantially view the saidtarget area and a video monitor and/or VCR capable of operation in arecord mode, the video camera substitution system comprising:

-   -   a failure detection means for detecting failure of the fixed        video camera;    -   a camera preset means having data concerning the position of the        target area with respect to the pan-tilt video camera; and,    -   a control means in operative association with the failure        detection means, the camera preset means and the pan-tilt video        camera, the control means being capable of controlling the        pan-tilt video camera for moving and setting the pan-tilt video        camera to monitor the target area when the failure detection        means detects failure of the fixed video camera so that the        target area is monitored substantially continuously.

It is an object of the present invention to provide a video recordersubstitution system for ensuring that video images and always recordedeven in the event of the failure of a video recorder including failureto record due to change-over of recording media and taking the videorecorder out of service.

In accordance with a still further aspect of the present invention thereis provided a video recorder substitution system for a video securitysystem comprising:

-   -   a first VRD for recording a video signal corresponding to a        target area;    -   a second VRD also capable of recording the video signal        corresponding to said target area;    -   a record failure detection means for detecting failure of the        first VRD to record said video signal, including failure due to        change-over of recording media and due to talking the video        recorder out of record its mode of operation; and,    -   a control means in operative association with the record failure        detection means, with the first VRD and with the second VRD, the        control means being capable of controlling the second VRD to set        the second VRD to record said video signal in the event that the        record failure detection means detects failure of the first VRD        so that the video signal corresponding to the target area is        recorded substantially continuously.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the present invention will now be describedwith reference to the accompanying drawings in which:—

FIG. 1.1 is block diagram of a video security system in accordance withthe present invention;

FIG. 1.2 is a set of waveforms showing the nature of insertion of asignal corresponding to text into the video signal;

FIG. 2 is a block diagram of an automatic VCR management system inaccordance with the present invention;

FIG. 3 is block diagram of a text insertion system in accordance withthe present invention;

FIG. 4 a is a block diagram of a prior art transmission cableequalisation system;

FIG. 4 b is a block diagram of a transmission cable equalisation systemin accordance with the present invention;

FIG. 5 is a block diagram of a video camera substitution system inaccordance with the present invention; and,

FIG. 6 is a perspective view of a PTZ camera in accordance with thepresent invention, shown with part of its housing shown in phantom

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) Video SecuritySystem

In FIG. 1 there is shown a Video Security System (VSS) 10 comprising anAutomatic VCR Management System (AVCRMS) 12, a Text Insertion System(TIS) 14, a Transmission Cable Equalisation System (TCES) 16 and a VideoCamera Substitution System (VCSS) 18.

The VSS 10 also comprises a plurality of fixed position cameras 20, aplurality of pan-tilt cameras 22, a plurality of video monitors 24, aplurality of VCRs 26, one or more standby VCRs 28 and a printer 30.

Typically, the VSS 10 is embodied in a computer system programmed toeffect various routines equivalent to the systems 12, 14, 16 and 18described herein.

Automatic VCR Management System

As shown in FIG. 2 the AVCRMS 12 comprises a controller 40 and aselector 42.

Typically the controller 40 is in the form of a computer programmed toeffect certain control functions as described herein. The controller 40is connected to a remote control input 44 of each of the plurality ofVCRs 26 and 28 and to an alarm output 46 of each of the VCRs 26 and 28.The controller 40 being capable of operating each of the VCRs 26 and 28via the remote control inputs 44 and also being capable of sensing analarm condition in each of the VCRs 26 and 28 via the alarm outputs 46.The controller 40 disabling any one of the VCRs 26 and 28 upon theoccurrence of an alarm signal at the alarm output 46 of that VCR 26 or28. The alarm condition becomes active when the VCR 26 or 28 is nolonger in a record mode of operation. This can happen due to failure ofthe VCR 26 or 28, the VCR 26 or 28 being taken out of service such as tochange a recording tape or to review a recorded tape or for repairs orthe like.

The selector 42 is typically in the form of a matrix video switch in,which any of its inputs 48 can be connected to any of its outputs 50, 52and 54. The output 50 is connected to one of the monitors 24, and theoutputs 52 and 54 are connected to record input 56 of two standby VCRs28. Each of the VCRs 26 and 28 has a play output 58 which is connectedto one of the video inputs of the selector 42 so that any video signalon any of the VCRs 26 or 28 can be displayed on the monitor 24. Theselector 42 is also connected via its inputs 48 to a plurality a videocamera outputs 60.

Typically, when one of the VCRs is detected as no longer being in arecord mode of operation the controller 40 causes an audible tone to begenerated and an alarm message is caused to be displayed on the monitor24. The message identifies which one of the VCRs 26 and 28 requiresattention. The controller 40 simultaneously selects the next availableone of the standby VCRs 28 and sets it to a record mode of operation viathe remote control input 44 and controls the selector 42 to direct thevideo signal from the relevant video camera output 60 to that VCR 28 forrecordal. The controller 40 also displays the identity of the videocamera and the VCR 28 onto which the video signal is now being recorded.Simultaneously, this information, along with the time and date and anyother special messages, are printed out on the printer 30.

Text Insertion System

As shown in FIGS. 2 and 3 the text inserter 14 is connected between thecamera outputs 60 and the inputs 56 of the VCRs 26. The text inserter 14is controlled by the controller 40 for the generation of text to beinserted into the video signal being recorded onto the VCR 26. Thecontroller 40 controls the insertion of the text into the video signalat a location which is not ordinarily part of the visible part of thevideo screen once displayed. Typically, the text data is inserted intothe horizontal line interval portion of the video signal (known as the“back porch” of the video signal).

The text inserter 14, particularly as shown in FIG. 3, inserts the textgenerated by the controller 40 into the video signal and is recordedonto the VCR 26 during recording. Due to the positioning of the textinto the video signal the text does not overly the normal viewableportion of the video signal. During playback of the video signal fromthe VCR 26 the text inserter extracts the text from the horizontal lineinterval of the video signal and reinserts it into the visible portionof the video signal so that the text can be seen on the monitor 24.

In the event that the text masks important parts of the video image onthe monitor 24 the text inserter 14 can be controlled by the controller40 to remove the text signal from the visible part of the video signal.Hence, the text recorded with the video image from the video cameras canbe removed from the video image seen on the monitor in the event that itmasks important parts of the video image.

It is important to note that the text is a data stream and not a videostream.

The recorded information can include time, date, source, equalisation,operator identification number, VCR identification number (since eachVCR has its own effective “fingerprint”) and the like. This informationis important in the scheme of irrefutably proving that the imagesrecorded by the VCRs are the events which actually took place.

Transmission Cable Equalisation System

As shown in FIGS. 1, 4 a and 4 b the transmission cable equaliser 16 isconnected between the video camera output 60 and the text inserter 14and is controlled by the controller 40.

The controller 40 has a conditioning signal (such as data) whichcharacterises the nature of the connection between each of a pluralityof video cameras 70 and the selector 42. This conditioning signal takesinto account any losses in the connection between the camera 70 and theselector 42 due to the nature of a connecting cable including itstransmission characteristics and its length. The conditioning signal isapplied to the equaliser 16 so as to alter the gain of the equaliser 16to allow for the losses inherent in the cable of each of the cameras 70.

Hence, only one equaliser 16 is required per monitor 24 rather than oneequaliser 16 per camera 70. In the event that a new camera 70 is addedto the video security system 10 the equalising requirements for thatcamera 70 are input into the controller 40 for controlling the equaliser16 when video signals from that camera 70 are being viewed on themonitor 24.

Video Camera Substitution System

The cameras 70 in the video security system 10 include fixed positioncameras 70 a and pan/tilt cameras 70 b (herein referred to as PTZcameras 70 b). Typically, a plurality of the fixed position cameras 70 aare directed at fixed targets in an area and a lesser number of the PTZcameras 70 b are spread out amongst the fixed position cameras 70 a sothat the PTZ cameras 70 b can substantially view the same field as theplurality of fixed position cameras 70 a and to be used to view movingtargets.

The video camera substitution system 18 is a part of the controller 40and has information concerning the relative positions of the PTZ cameras70 b and the fixed position cameras 70 a. The information includes whichof the PTZ cameras 70 b are capable of covering the viewing areas ofeach of the fixed position cameras 70 a. The controller 40 is connectedto the PTZ cameras 70 b via a communication control module 74 so that inthe event that a particular one of the fixed position cameras 70 aceases to operate the controller can automatically determine which oneof the PTZ cameras 70 b can be used in its place and then control thePTZ camera 70 b via its controller 76 to pan, tilt, zoom and focus toview the target viewed by the camera 70 a which failed.

The VCSS 18 also has a keyboard 78 connected to the controller 40 forallowing manual operation of the PTZ cameras 70 b to view targets at thewill of an operator of the keyboard 78. For this purpose the keyboard 78conveniently includes a joy stick 80.

Multiple Rotation Video Camera

The PTZ cameras 70 b comprise a conventional camera 100 set on atransport mechanism 102 which is capable of rotating greater than 360°such as about 1000°.

The camera 100 has a lens 110 which has a zoom facility and whose iriscan be adjusted for changes in lighting levels.

The transport mechanism 102 has a housing 120, a frame 122, a verticalaxis drive unit 124, a horizontal axis drive unit 126 and control unit128.

The housing 120 comprises a ceiling mount 140, a camera mask 142 and atransparent cover 144.

The ceiling mount 140 is typically fixed into a ceiling of a building(although it could be fixed to a wall or the like) so that the cameramask 142 and the transparent cover 144 are disposed below the ceilingfor allowing the camera 100 viewing within a room under the ceiling. Theceiling mount 140 is typically made from anodised aluminium and istypically cylindrical in cross-section.

The camera mask 142 is attached to the frame 122 and hence is able torotate with respect to the ceiling mount 140. The camera mask 142 has aslot 150 which is dimensioned to allow the lens 110 to have a clearuninterrupted view through it. The slot 150 extends substantially from ahorizontal position with respect to the lens 110 to a verticallydownward position with respect to the lens 110. Hence, the lens can bemoved from a horizontal viewing position to a vertically downwardviewing position in the slot 150. The camera mask 142 has a plurality oflugs 152 for use in releasably attaching the camera mask 142 to clips154 of two mask mounts 156 (one of which is shown) of the frame 122.

Typically, the camera mask 142 is coloured black so as to avoidreflecting light from it. The purpose of the camera mask 142 is torotate with the camera 100 to mask observation of the viewing positionof the camera 100. We have discovered that due to the darkness of thecamera mask 142 the viewing position of the camera 100 is substantiallyunobservable.

The transparent cover 144 is attached to the ceiling mount 140 andlocated outside of the camera mask 142. The purpose of the transparentcover 144 is to shield the camera 100 and the interior of the transportmechanism 102 from the elements. In this manner the cover 144 can behermetically sealed to the ceiling mount 140 and the PTZ camera 70 b canbe located out doors.

The frame 122 comprises a top plate 160, two brackets 162 and 164 and amoveable platform 166. The top plate 160 is disposed horizontally and isable to rotate inside the housing 120. The brackets 162 and 164 arefixed to the top plate 160 and disposed vertically downwardly therefrom.The platform 166 is conveniently substantially U-shaped and pivotablyattached to lower ends of the brackets 162 and 164. The pivotableattachment is via a pivot bolt 170 located through the bracket 162 and apivot axle 172 located through the bracket 164 The platform 166 has aplurality of fixing slots 176 for mounting the camera 100 onto it. Thefixing slots 176 are typically disposed parallel to the brackets 162 and164.

The vertical axis drive unit 124 comprises a drive motor 180 with adrive cog 182, a toothed cog 184 and a toothed belt 186. The toothed cog184 is releasably secured to the ceiling plate 140, such as by holes(not shown) in a top 188 of the toothed cog 184. The drive motor 180 isattached to the top plate 160 of the frame 122. The drive motor 180 isdriven by electrical signals from the control unit 128 for producingrotation of the drive cog 182. Since the toothed cog 184 is stationarywith respect to the ceiling mount 140 rotation of the drive cog 182causes the frame 122 to rotate within the housing 120. The speed ofrotation of the frame 122 is dependent upon the speed of the drive cog182 and the angle of rotation is dependent upon the time for which thedrive motor 180 receives signals from the control unit 128.

The horizontal axis drive unit 126 comprises a drive motor 200 with adrive cog 202, a toothed cog 204 and a toothed belt 206. The toothed cog204 is fixed to the platform 166 so that rotation of the toothed cog 204produces pivoting of the platform 166. The drive motor 200 is mountedonto the bracket 164 and the drive cog 202 drives the toothed belt 206for driving the toothed cog 204. The toothed cog 204 has a stop 210located in it for limiting the pivotable travel of the platform 166 soas to protect the camera 100 from damage which may otherwise occur. Thedrive motor 200 is controlled by signals from the control unit 128 forpivoting the lens 110 of the camera 100 in the slot 150 of the cameramask 142 as indicated by arrow 212. Typically, the horizontal drive unit126 allows pivoting of the platform 166 from substantially horizontal tosubstantially vertical.

The control unit 128 has a horizontal control unit and a verticalcontrol unit. Each of the horizontal and vertical control units has aposition sensor device for determining the position of the toothed cogs204 and 184 respectively. Typically, the position sensor device is ahole located in the toothed cog 184, 204 and the control unit are ableto count up and down from the position of the holes for determining themovement of the cogs 184, 204.

We have discovered that in order to quickly move the camera 100 from oneviewing position to another, and to keep accurate count of the actualposition of the camera 100 there are some physical constraints whichmust be allowed for. Principally this involves controlling the drivemotors 180 and 200 so as not to exceed maximum rates of acceleration anddeceleration and not to exceed a maximum speed. Also, and mostimportantly, we have discovered that the drive motors 180 and 200 needto be controlled so as to have a period of substantially zeroacceleration between periods of acceleration and deceleration. This isrequired because otherwise there is a very large change in the momentumof the transport mechanism 102 required in switching from accelerationto deceleration. The result of such abrupt changes in the accelerationof the transport mechanism is the control unit 128 looses count of theposition of the toothed cogs 184 and 204 and thus inaccuracies in thelocation of the camera 100 are experienced.

Hence, the control unit 128 is programmed to limit the maximum rate ofacceleration and deceleration of the drive motors 180 and 200 and toprovide a minimum period of substantially zero acceleration betweenperiods of acceleration and deceleration. The control unit 128 then usesthese limits to drive the transport mechanism 102 between viewinglocations whilst accurately reaching those viewing locations.

The PTZ camera 70 b is, in one embodiment, connected to the remainder ofthe video security system 10 by a plurality of cables. The cables carryvideo signals, control signals and electrical power. In order to allowthe transport mechanism 102 to rotate through greater than 360° thecables are arranged in a loop so that they can be twisted three or fourtimes without damage. This allows the vertical axis drive unit 124 torotate the platform 166 through a total angle of about 1000°.

The control unit 128 has a counter to count up and down depending uponthe position and motion of the drive motor 180. Typically, the counterincrements the count by 4000 for each 360° of rotation. By such countingthe control unit 128 can be aware of how far the transport mechanism 102is away from its ultimate end of travel. The control unit 128 isprogrammed such that when the camera 100 is not engaged in tracking amoving event it unwinds to proximate the middle of its 1000° of angulartravel. In this way the chances of the transport mechanism 102 reachingits ultimate angular travel is greatly reduced.

In another embodiment slip rings are used for each cable, which thenallows the vertical axis drive unit 124 to rotate the platform 166through an infinite angle of rotation.

Hence, the PTZ camera 70 b can be used to follow a target even where thetarget travels through an angle of greater than 360° and hence thechances of the PTZ camera 70 b being run up against its limits ofrotation are greatly reduced and the ability to follow a target as itmoves through an area is greatly enhanced.

Switching Between Viewing Locations

The controller 40 controls the PTZ cameras 70 b to move back and forthbetween a plurality of viewing locations so that the camera can monitora plurality of fixed locations.

The PTZ camera 70 b comprises a video lens 110 and camera 100, a zoomcontrol, a focus control, a pan control, a tilt control and a cameraposition controller (included in the controller unit 128—FIG. 6).

The video lens and camera is settable to view a target. For example, thetarget could be a person at a gaming table in a casino. The video lenshas a machine readable signal corresponding to its zoom and focussetting. The zoom and focus controls allow adjustment of the zoom andfocus of the video lens and camera.

The pan and tilt controls control the pan and tilt of the video lens andcamera about substantially vertical and horizontal axes for viewingtargets typically in a region of 360° about the PTZ camera. The pan andtilt controls each have a machine readable signal corresponding to theirsettings.

The camera position controller is coupled to respond to the machinereadable signals from the video lens and camera, the zoom and focuscontrols and the pan and tilt controls. The camera position controllercontrols the settings of the video lens, the zoom and focus controls andthe pan and tilt controls for viewing the targets within the viewingregion automatically under the instruction of an operator.

The camera position controller has a first memory register (such aslocated in a computer) to store the values of the machine readablesignals corresponding to the settings of the video lens and camera, thezoom and focus controls and the pan and tilt controls. The first memoryregister stores the values of the settings corresponding to a firstlocation of temporary interest, such as the location of a handbag. Thecamera position controller also has a second memory register for storingthe values corresponding to a second location of temporary interest,such as the location of a suspected felon who is believed to be about tosteal the handbag.

The camera position controller has a toggle button which is operable tocause the values of the settings of the video lens and cameracorresponding to the second location to be recalled from the secondmemory register and loaded into the video lens and camera whilst thevalues corresponding to the first location are removed from the videolens and camera and stored into the first memory register. The togglebutton is also operable to cause the values of the settings to beupdated in the event that one of the targets moves or the operatorchooses a new target of temporary interest. The toggle button alsoallows for switching viewing between the two locations of temporaryinterest. By so doing the camera position controller can control thevideo lens and camera to view between two (or more) desired locationswithout continual manual re-adjustment of the video lens, the zoom andfocus controls or the pan and tilt controls.

In use, an operator can set a desired location of temporary interest tobe monitored by the video lens and camera. The video lens 110 and camera100 can then be manually moved to view another location of temporaryinterest and the video lens 110 and camera 100 can then by toggledbetween the two viewing locations by the operation of the toggle button.

To achieve this the operator first manually pans and tilts the videolens 110 and camera 100 to view a first target at a first location oftemporary interest. Then the operator manually adjust the zoom and focusof the video lens 110 and camera 100 for the target. The operator thenpresses the toggle button to store the values of the settings of thezoom and focus controls and the pan and tilt controls into the firstmemory register. The operator can then manually control the zoom andfocus controls and the pan and tilt controls for setting the video lens110 and camera 100 to view a second target at a second location oftemporary interest. When the operator again presses the toggle buttonthe values of the settings corresponding to the second location arestored into the second memory register and the values of the settingscorresponding to the first viewing location are recalled from the firstmemory register and used to control the video lens 110 and camera 100.Once the values are exchanged the camera position controller controlsthe zoom and focus controls and the pan and tilt controls to repositionthe viewing location of the video lens 110 and camera 100.

The location of the targets can be updated by manually adjusting thezoom and focus controls and the pan and tilt controls for the video lens110 and camera 100 and pressing the toggle button again to update thevalues stored in the relevant memory register. That is, when no manualadjustments are made to the settings of the video lens 110 and camera100 the toggle button causes toggling between the two locations oftemporary interest, but when manual adjustments are made to the settingsof the video lens 110 and camera 100 the toggle button causes updatingof the values of the settings.

Thus a PTZ camera can be used to monitor two fixed locations within aviewing area, as well as to operate under fully manual control. Hence,the PTZ camera of the present invention is the equivalent of two fixedposition cameras which can be set to view locations of temporaryinterest and which can be set to new locations of temporary interest asdesired by an operator. That is, the PTZ camera function as theequivalent of two dynamically positioned fixed cameras. Also, the changetime in changing between the two viewing locations is about the same asthe time involved in changing viewing between two fixed cameras (thatis, less than 1 second).

Typically, the camera position controller is configured to set the lastviewing position as being any position at which the operator stopped forgreater than, say, 1 second.

This facility could be configured into a logical data stack so that thelast, say 10, viewing positions could be stored in memory are recalledsequentially (this feature is herein referred to as “back up”).

Modifications and variations such as would be apparent to a skilladdressee are considered within the scope of the present invention. Forexample, the camera position controller could have a single switch tocontrol toggling between two camera locations. Also, the iris setting ofthe video lens and camera could also be controlled.

1. A text insertion system for a video security system having a videocamera and a video monitor and/or a VRD capable of operation in a recordmode, the text insertion system comprising: a text insertion meansconnected between the video camera and the video monitor and/or VRD forinserting a text signal into a video signal received from the videocamera for display on the video monitor and/or recordal by the VRD, theinsertion of the text signal being timed within the back porch of thevideo signal so that the text signal does not alter the visible part ofthe video frame of the video signal; a control means connected to thetext insertion means, the control means generating the text signal andsending the text signal to the text insertion means; and, a playbackmeans operatively associated with the text insertion means and thecontrol means, the playback means responding to the text signal portionof the video signal, the playback means having a text signal displaymeans for rendering the text signal visible on the video monitor, and atext signal hiding means for rendering the text signal non-visible onthe video monitor, the text signal display means and the text signalhiding means being operable by a person using the text insertion systemto allow alternating between showing text corresponding to the textsignal on the video monitor and showing on the video monitor that partof the video frame which would otherwise be obscured by the text, andthe playback means being able to make the text signal visible or hiddenduring both recording and playback modes of operation of the VRD.
 2. Atransmission cable equalisation system for a video security systemhaving a plurality of video cameras and a video monitor and/or a VRDcapable of operation in a record mode, the transmission cableequalisation system comprising: a selector means connected between thevideo cameras and the video monitor and/or VRD for selecting videosignals from the video cameras to be directed to the video monitorand/or VRD so that the video signal from one video camera is display onthe video monitor and/or recorded on the VRD at a time; an equalisermeans connected between the selector means and the video monitor and/orVRD for equalising the video signal from losses caused by the nature ofthe connection between each of the video cameras and the selector means;and, a control means connected to the equaliser means and the selectormeans, the control means having a reference means having dataquantifying the losses between each video camera and the selector means,and the control means controlling the equaliser means to compensate forthe losses associated with each video camera as its video signal isdisplayed on the video monitor and/or recorded on the VRD so that thecondition of the video signal at the video monitor and/or VRD isequalised substantially independent of the characteristics of theconnection between the video camera and the selector means so that onlyone equalisation means is required per video monitor and/or VRD insteadof one equalisation means per video camera.
 3. A video camerasubstitution system for a video security system having a fixed videocamera for viewing a target area, a pan-tilt video camera capable oforientation to substantially view the said target area and a videomonitor and/or VRD capable of operation in a record mode, the videocamera substitution system comprising: a failure detection means fordetecting failure of the fixed video camera; a camera preset meanshaving data concerning the position of the target area with respect tothe pan-tilt video camera; and, a control means in operative associationwith the failure detection means, the camera preset means and thepan-tilt video camera, the control means being capable of controllingthe pan-tilt video camera for moving and setting the pan-tilt videocamera to monitor the target area when the failure detection meansdetects failure of the fixed video camera so that the target area ismonitored substantially continuously.
 4. A video recorder substitutionsystem for a video security system comprising: a first VRD for recordinga video signal corresponding to a target area; a second VRD also capableof recording the video signal corresponding to said target area; arecord failure detection means for detecting failure of the first VRD torecord said video signal, including failure due to change-over ofrecording media and due to taking the video recorder out of record itsmode of operation; and, a control means in operative association withthe record failure detection means, with the first VRD and with thesecond VRD, the control means being capable of controlling the secondVRD to set the second VRD to record said video signal in the event thatthe record failure detection means detects failure of the first VRD sothat the video signal corresponding to the target area is recordedsubstantially continuously.
 5. A video recorder substitution systemaccording to claim 4, in which there are a plurality of first VRDs and aplurality of second VRDs so as to facilitate management of recordingfrom a plurality of video cameras.
 6. A video recorder substitutionsystem according to claim 4, also including a log generating means forproducing a log of data corresponding to which VRD the video signal fromeach video camera was recorded onto so as to enable the video signalrecorded onto a plurality of recording media on a plurality of VRDs tobe retrieved and reviewed.